1. Field of the Invention
The present invention relates to a head assembly employed in a recording medium drive such as a hard disk drive (HDD), and in particular, to a head assembly utilizing a so-called microactuator capable of moving or shifting a head in a recording medium drive.
2. Description of the Prior Art
Japanese Patent No. 2528261 and Japanese Patent Application Laid-open No. 11-31368 disclose a well-known type of hard disk drives (HDDs), representing a magnetic recording disk drive, including a head suspension supported at the tip end of a carriage horizontally extending. The head suspension is movable relative to the carriage which is allowed for swinging movement around the vertical axis. The mentioned HDD allows the carriage to swing so as to achieve a seeking action of a read/write head related to a target recording track. The carriage is also supposed to cooperate with the head suspension for forcing a read/write head to follow the target recording track in a tracking operation. A microactuator, such as a piezoelectric element, is interposed between the carriage and the head suspension so as to cause a relative swinging movement between the carriage and the head suspension.
In general, a so-called servo control is utilized to achieve a tracking operation. The servo control usually achieves a feedback control of the microactuator based on a signal supplied from a read/write head. The signal serves to represent a deviation amount of the read/write head from a target recording track. If a high frequency component is introduced in the driving voltage supplied to the microactuator in the feedback control, the head suspension suffers from a mechanical or physical resonance or vibration, so that the tracking action of the read/write head may be hindered. A reliable or stable tracking operation cannot be achieved. The high frequency component may inevitably be generated based on the feedback signal following a frequent variation in the deviation amount of the read/write head, for example. Otherwise, the high frequency component may be found as a noise in the output of an amplifier designed to amplify the driving voltage.
It is accordingly an object of the present invention to provide a head assembly and/or a recording medium drive capable of stabilizing, with a simple structure, the tracking action of a head during a servo control of an microactuator.
According to a first aspect of the present invention, there is provided a recording medium drive comprising: a recording medium; a head related to the recording medium; a driven member supporting the head; a support member designed to support the driven member for a relative movement; a microactuator interposed between the driven member and the support member so as to cause the relative movement between the driven member and the support member based on a driving voltage; a voltage source generating the driving voltage following variation in a feedback signal generated based on a position of the head relative to the recording medium; and a resistor interposed in serial between the voltage source and the microactuator.
The microactuator is allowed to operate in response to supply of the driving voltage so as to position the head with respect to a target recording track on the recording medium in the recording medium drive. The driving voltage is designed to follow variation in the feedback signal, so that a tracking action of the head related to the target recording track, namely, a servo control of the driven member can be achieved. When a piezoelectric element or a so-called capacitance actuator is utilized in the microactuator, for example, the microactuator is inevitably forced to function as a capacitance. A combination of the microactuator and the resistor enables establishment of a so-called low pass filter. As a result, a high frequency noise involuntarily introduced in the driving voltage can be eliminated or removed from the driving voltage. In general, the driven member has a natural frequency of a relatively higher frequency in the recording medium drive because of its weight or mass. Elimination of the high frequency noise enables a reliable prevention of the mechanical or physical resonance or vibration resulting from the weight or mass of the driven member and the like. It should be noted that the microactuator may comprise any structure equivalent to a capacitance in addition to the aforementioned piezoelectric element and capacitance actuator.
It is preferable that the resistor is inserted in a driving signal line attached to the support member for carrying the driving voltage to the microactuator. In general, the driving signal line is often disposed adjacent a data signal line for carrying data signals of the head. If the resistor can be located closer to the microactuator in the driving signal line, the resistor is allowed to eliminate an electromagnetic noise leaking out of the data signal line and/or a motor for driving the recording medium. As a result, the servo control can further be stabilized.
In addition, according to a second aspect of the present invention, there is provided a head assembly comprising: a plurality of heads; a plurality of driven members respectively supporting the head; a common support member designed to support the driven members for a relative movement; data signal lines attached to the support member for carrying a data signal of the head; a microactuator interposed between the individual driven member and the support member so as to cause the relative movement between the individual driven member and the support member based on a driving voltage; a driving signal line attached to the support member for carrying the driving voltage to the microactuator; and a resistor inserted in the driving signal line between the microactuator and a voltage source of the driving voltage.
In the same manner as the first aspect, the microactuator is allowed to operate in response to supply of the driving voltage so as to achieve a tracking action of the individual head related to the target recording track, namely, a servo control of the driven member. When a piezoelectric element or a so-called capacitance actuator is utilized in the microactuator, for example, the microactuator is inevitably forced to function as a capacitance. A combination of the microactuator and the resistor enables establishment of a so-called low pass filter. As a result, a high frequency noise involuntarily introduced in the driving voltage can be eliminated or removed from the driving voltage in the aforementioned manner.
In particular, the driving signal line may comprise: a common driving signal line extending from the voltage source to a branch point so as to accept interposition of the resistor; and a plurality of branch driving signal lines respectively extending from the branch point to the individual microactuator. If the single resistor is assigned to a group of the branch driving signal lines, less resistors are required, as compared with the case where the resistors are inserted in every driving signal line. Cost reduction can be achieved.
Further, according to a third aspect of the present invention, there is provided a head assembly comprising: a piezoelectric element deforming in response to supply of a driving voltage; first and second electrodes holding the piezoelectric element therebetween and leading the driving voltage to the piezoelectric element; a conductive adhesive layer interposed between the piezoelectric element and at least one of the first and second electrodes; a driven member fixed to the first electrode so as to support a head; a support member fixed to the second electrode; and a driving signal line connected to the first and second electrodes so as to lead the driving voltage to the first and second electrodes.
In the head assembly, the resistor of a predetermined resistive value can easily be obtained by properly selecting the material of conductive powders contained in the conductive adhesive layer and/or adjusting the amount of the conductive powder. Employment of such a resistor comprising the conductive adhesive layer serves to locate the resistor closest to the piezoelectric element, so that the resistor made of the conductive adhesive is allowed to reliably eliminate or remove a high frequency noise involuntarily introduced in the driving signal line. A conductive adhesive containing a predetermined amount of conductive powder may be injected between the first electrode and the piezoelectric element as well as between the second electrode and the piezoelectric element so as to form the conductive adhesive layer interposed between the piezoelectric element and at least one of the first and second electrodes. When the injected conductive adhesive is cured or hardened, the conductive adhesive layer can be obtained.
Furthermore, according to a fourth aspect of the present invention, there is provided a recording medium drive comprising: an enclosure defining an inner space; a recording medium disposed within the inner space; a head disposed within the inner space with respect to the recording medium, a driven member supporting the head; a support member designed to support the driven member for a relative movement; a microactuator interposed between the driven member and the support member so as to cause the relative movement between the driven member and the support member based on a driving voltage; an amplifier amplifying a voltage from a voltage source so as to generate the driving voltage; and a DC/DC converter disposed outside the inner space and designed to supply a source voltage to the amplifier.
In general, the DC/DC converter is well known to generate or radiate a high frequency noise. The high frequency noise tends to be introduced in the driving voltage carried along the driving signal line. Also, the high frequency noise may directly act on the driven member so as to induce a mechanical resonance of the driven member. When the DC/DC converter isolated by the enclosure from the inner space in this manner, a high frequency noise leaking out of the DC/DC converter cannot reach the driven member and the driving signal line within the inner space. As a result, a stable servo control for the driven member can further be improved.
The recording medium drive of the invention may include a magnetic disk drive such as a hard disk drive (HDD), a diskette drive (FDD), and the like, an optical disk drive employing an optical medium such as a compact disk (CD), a digital video disk (DVD), and the like, a magneto-optical disk (MO) drive, and any other types. In particular, the head assembly of the invention can be applied to any of the aforementioned recording medium drives. Moreover, the microactuator of the invention may be interposed not only between a carriage and a head suspension, but also between a head suspension and a head slider as well as between a head slider and a head element, in any of the aforementioned recording medium drives.